Liquid fuel storage tanks deployed underground have associated with them one or more risers or pipes leading to an above ground location. A riser is employed to fill the tank.
Various structures such as tanker truck nozzle receptacles (an example being the swivel adaptor/receptacle shown in my U.S. Pat. No. 6,517,356), and spill containment vessels (an example being the spill containment system shown in U.S. Pat. No. 4,696,330 of which I am a co-inventor) are typically threadedly engaged with an upper threaded end of the riser.
It is important that a fluid-tight connection be established between the upper riser end and the structure. This becomes a problem when, as is often the case, the upper end of the riser is “field made”, that is, fabricated on site. Often the upper distal ends of “field made” risers are rough or irregular. Non-field threaded upper distal ends can also be irregular or damaged. In such circumstances it is difficult, and in some cases impossible, to establish a fluid-tight sealing surface between the riser and structure threadedly engaged therewith.